Reliable and efficient performance of radio transmission systems used in telecommunications activities depend on the optimum utilization of the available radio spectrum within a geographic area. Optimum utilization is achieved by conducting spectrum analysis between existing radio systems and any new systems to be installed. Computer based systems have been developed to assist radio engineers in their spectrum analysis activities.
To conduct a spectrum analysis, first, one must calculate the signal power of a signal intended to be received at a specified location (hereinafter "C") and then, all undesired signals that can also be expected to be received at the receiver location (hereinafter "I"). The ratio (C/I) of the intended signal level to the interfering signals is then calculated and compared to minimum tolerance values, called signal to noise ratio objectives, which are established according to the specification of the radio receiver under study. If the calculated ratio is larger than the objective, then the radio system is deemed to be able to be operated efficiently (i.e. operate without interference from other systems that would hinder transmission performance of the system under study). If the calculated ratio is smaller than the objective, than the performance of the transmission system under study will be affected and some engineering choices must be made. These could include increasing the transmission power of the new system, or a new site placement for the receiver.
Calculating the received power of a radio transmission is a complicated calculation requiring the incorporation of many factors into the analysis. These factors include such items as antenna height, the terrain clearance, the free path space loss, antenna gain, multipath fading, and the attenuation due to water vapor absorption. Algorithms for computing radio propagation path loss are well known in the art. In fact, the National Telecommunication Information Agency, an agency of the U.S. Department of Commerce, has published Technical Note 101, in 1976, which provides a detailed set of methods and algorithms and technical data used by radio engineers in computing the path loss for microwave radio transmission systems. This Technical Note is comprehensive compilation of technical data and contains many complicated propagation algorithms that have been encoded into computerized radio engineering systems.
One such computerized system used by engineers in the Regional Bell Operating telephone companies is called the Microwave Radio and Satellite Engineering and Licensing System II (MRSELS-II) developed by Bell Communications Research Inc. This system conducts the spectrum analysis after specified inputs are provided by the radio engineers. The analysis is conducted in two phases. The first is a conservative automated study based on a line-of-site transmission model that identifies existing transmitters that may potentially interfere with a proposed new receiver. This conservative automated study overestimates the power of the signals from other transmitters to eliminate from consideration, as potential interfering systems, those that will not in practice, interfere.
In the second phase, as a second step, a detailed analysis is conducted on the potential interfering systems using the more accurate propagation models from Technical Note 101 that require the use of detailed terrain information. The terrain information is provided by the 3 second U.S. Geological Survey terrain database. This more detailed analysis must be repeated for each potential interfering system. Experience has shown that 80 to 90% of the systems that are identified as potential interfering systems during the first step are found to not interfere after the more detailed analysis is conducted incorporating terrain data. Consequently, significant computer and manpower resources are wasted conducting detailed studies on systems that have little likelihood of causing problems when the terrain information is included.
Therefore, it is an object of my invention to provide a method and system that will reduce the number of cases of potentially interfering systems that require a more detailed analysis without being as computationally intensive as the prior art systems.